The present invention relates to an optical apparatus for a fingerprint identification system, and more particularly to an optical apparatus for a fingerprint identification system which improves the accuracy of fingerprint identification by allowing the user to observe his magnified fingerprint image by virtue in a magnifying glass of the optical apparatus.
Conventionally, optical apparatus used for fingerprint identification system identifies a fingerprint by using the properties of emitted beam from a light source, being absorbed at ridges and being reflected at valleys of the fingerprint of an individual finger laid on a slanted surface of a triangular prism.
Known fingerprint identification systems (hereinafter, referred to collectively as "conventional optical apparatus") can be generally classified into two types, a monitor type of optical apparatus, such as for a computer system security, which is connected to a computer system so as to allow the fingerprint to be observed by means of a monitor of the computer system, and an individual type of optical apparatus without using such a monitor. The above types of conventional optical apparatus will be more described in detail as follows.
FIG. 1A is a schematic view showing the construction of a representative embodiment of the known monitor type of optical apparatus. This type of optical apparatus comprises a light source 1 for emitting a light beam to the subject fingerprint "P", a triangular prism 2 including a slant surface 2a of about 45.degree. inclination angle on which the fingerprint "P" is laid, an image producing lens system 3 for receiving the reflected light beam from the valleys of the subject fingerprint laid on the prism 2 and then producing an image of the subject fingerprint "P", an area charge coupled device 4 (hereinafter, referred to simply as "the area CCD") for converting the produced fingerprint image into an electric signal, an amplifying/analyzing circuit 5 (Signal Processing Circuit) for amplifying and then analyzing the electric signal for the subject fingerprint provided by the area CCD 4, and a monitor 6 for displaying the fingerprint image Q in a binary coded form by virtue of the amplifying/analyzing circuit 5.
In identifying operation of the above type of optical apparatus, upon seeing the binary coded fingerprint image Q displayed on the monitor 6 simultaneously with laying his finger being identified on the slant surface 2a of the prism 2, the user slowly slides the finger from the initial position to a subject position consistent with same position as that of the fingerprint registration so that the identifying position of the subject fingerprint can be adjusted to be the registered position and the subject fingerprint can be thus identified as the same fingerprint as that of the registration by virtue of the amplifying/analyzing circuit 5 which amplifies and analyzes the electric signal from the area CCD 4.
On the other hand, the known individual type of optical apparatus has the same elements and operational theory as those of the above mentioned monitor type of optical apparatus shown in FIG. 1A except for including a finger guide member shown in FIG. 1B. The guide member is mounted on the slant surface 2a of the prism 2 and adapted for guiding the finger by virtue of the mechanical structure thereof. Also, this type of optical apparatus has no monitor 6 unlike the above monitor type of optical apparatus. As illustrated, the finger guide member comprises a U-shaped support wall 7 mounted onto the slant surface 2a of the prism 2, a rounded stopper 8 for restraining further movement of the finger F in the X-axial direction on said slant surface 2a, and a pair of movable side guiders 10 and 10' each movably elastically mounted to the U-shaped support wall 7 by virtue of compression coil springs 9, 9' and adapted to elastically restrain the movement of the finger in the Y-axial direction.
In operation, this type of optical apparatus restrains the fingerprint being identified at a position on the slant surface 2a of the prism 2 by means of the stopper 8 and the movable side guiders 10 and 10', and produces the fingerprint image, converts the produced fingerprint image into an electric signal and generates the electric signal binary coded by virtue of the amplifying/analyzing circuit 5, by way of the same process as that of the monitor type of optical apparatus, thereby accomplishing the fingerprint identification.
However, the known monitor type of optical apparatus has a disadvantage in that it displays the binary coded fingerprint image by means of a digital display system, the monitor 8, so that it needs a considerably longer time for adjusting the identifying position of the subject fingerprint to the registered position than that of a direct adjusting process in that the user adjusts the identifying position of the fingerprint simultaneously with seeing the practical fingerprint image. Also, the known individual type of optical apparatus has a disadvantage in that if there an error occurs in the fingerprint identification as a result of a positional difference between the registered fingerprint position and the inputted fingerprint position, it is very difficult to adjust the identifying position of the fingerprint because of the impossibility of confirming the previous identifying fingerprint position.